The latter half of the twentieth century has been witness to a phenomenon known as the information revolution. While the information revolution is a historical development broader in scope than any one event or machine, no single device has come to represent the information revolution more than the digital electronic computer. The development of computer systems has surely been a revolution. Each year, computer systems grow faster, store more data, and provide more applications to their users.
The declining prices and expanding capabilities of modem computers cause them to be applied to an ever increasing variety of applications. For some years now, inexpensive “personal computers” have been available for personal use at home or for the use of a single individual at a place of business. Increased miniaturization has made it possible to design portable “laptop” computers, having essentially the same functions as desktop personal computers.
In recent years, a family of portable digital devices known as palm-tops or personal digital assistants (PDA), have been introduced. Generally, these devices are digital computing devices, but may have somewhat more limited function than the laptop or desktop personal computers. A PDA device typically contains a very small display and a very restricted keyboard for data entry when compared with the laptop or desktop. I.e., the display either shows data in a very reduced size, or more typically, shows less data that would be visible in the display of a typical desktop system. Additionally, the keys may be very small and/or limited in number, so that touch typing is not practical. These are design sacrifices which are made to reduce the size of the device to something than will fit in the palm of one's hand.
One of the limitations of a typical PDA device is the manner in which the data in the PDA can be output in “hardcopy” form (i.e., printed on paper or other medium). A conventional printing device includes a paper feed mechanism, a print head, and a moveable carriage for moving the print head relative to the paper. Such a design necessarily implies that the printing device is at least as wide in one dimension as the width of the paper. Since it is desirable to provide output on standard 8½″×11″ paper or on standard A4 paper, a conventional printer is typically more than 8½ inches wide. This dimension is generally considered too large for an acceptable PDA device.
PDA designers have followed several different approaches to providing hardcopy printed output. PDA devices are commonly provided with an interface for receiving data from and sending data to another digital device. Data can therefore be transferred to another device via this interface, and the other device can print the data. The other device may be, e.g., a desktop personal computer having an attached printer, a stand-alone print station, or some other digital device. Although this approach does make it possible to print data from a PDA device, there are obvious limitations. The device which receives and prints the data is generally not portable, and therefore, it will not always be conveniently available to the PDA user when the user wishes to print something from the PDA. Additionally, the need to transfer data through another device for printing opens up a series of compatibility issues, e.g.: Is the receiving device capable of correctly handling communications with the PDA communications program? Does the receiving device have the required application software, and at the correct version and level, for printing the data? Does the receiving device have adequate storage capacity?
Another approach is to provide a dedicated digital printing device as an optional accessory to the PDA. Generally, the printing device attaches to the PDA via a cable, and receives and prints data directly from the PDA. This approach resolves most of the potential compatibility issues that may be involved in transferring data to another computer system for printed output, but it still suffers from the lack of portability. Such an optional printing accessory is still at least as wide as the paper, and therefore not intended to be carried around on the person as a PDA is. As a result, the printing accessory usually is left in a fixed location (such as the user's home or office), and is not available for use when the user is away from this fixed location.
Another approach is to provide a built-in print mechanism in the PDA, which prints on very narrow paper (usually from a roll). This solves the problem of portability, but the output medium is often of very limited value. Most documents are formatted for wider paper, and printing on such a medium means either re-formatting the document so that it doesn't look the same, or shrinking the typefonts to the point of illegibility. Finally, even such a narrow, limited function printing device adds significantly to the weight and size of the PDA.
A PDA has the potential to function as an indispensable accessory of the user that is carried everywhere, much like a wallet or purse. Ideally, the user would maintain all manner of useful information and applications on the PDA, to be available instantaneously, anywhere. However, this potential is impaired if the user must return to some fixed location to obtain hardcopy output from the PDA. A need exists for an improved technique for printing information from a portable digital device.
Although not used in PDA devices, portable hand-held printing devices for printing labels, bar codes, and the like are also known. Like other conventional printing devices, the printable image produced by such devices is constrained by the physical size of the device. An example of such a portable printing device is shown in U.S. Pat. No. 5,825,995 to Wiklof, et al.
A further need exists for a simple, portable automated printing device which is freed from the dimensional constraints of conventional print carriage mechanisms, and can thus print on paper or other media of arbitrary size significantly larger than the printing device itself.